Lighting source: comprised by N units of LED, it is the main part of the lighting fixture. It can produce the light.

LED driver: Since the working voltage of every single LED is very low (between 2.8 -3.6VDC), and the range of the working voltage is very small, LED cannot work by normal voltage. It has to control the input power to constant voltage and constant current by circuit. LED driver will directly affect the lifespan of LED and the LED lighting fixture.